The review of the Plebejus argyrognomon (Bergstrasser, [1779]) species group from the East Palaearctic. Part 1: Valuable characters of the male genitalia, Plebejus mongolicus (Rühl, [1893]), P. pseudaegon ussuricus (Forster, 1936) and P. transbaicale

The paper presents the first part of the review of the Plebejus argyrognomon (Bergstrasser, [1779]) species complex focused on the territory of the East Palaearctic. The general characters of the male genitalia are discussed, taxonomically valuable sclerites are pointed out. The male genitalia of P. maracandicus (Erschoff, 1874), P. argyrognomon and P. caspicus (Forster, 1936) are described and figured, the species status of the taxon caspicus is confirmed. Three eastern species are reviewed: P. mongolicus (Rühl, [1893]), P. pseudaegon ussuricus (Forster, 1936) and P. transbaicalensis (Kurentzov, 1970), stat. nov. Two new subspecies are described: P. mongolicus okianus ssp. nova (type locality: Russia, Buryatia, East Sayan, Oka Valley) and P. m. barguzin ssp. nova (type locality: Russia, Buryatia, Barguzin Valley).